A.J.
Definitely not easy...I struggle with this too. Especially after the new baby comes and you're sleep deprived and would much rather nap than get in a workout (sleep is important for health too!).
I agree with all the following below, best options are to find things you can do with the kids. My favorite thing to do in the summer is take the kids for a walk in a double stroller (or jog if you're into that). Not only did they love the fresh air, but I get an added bonus of pushing 40+ pounds around the neighborhood. Sometimes I would let my toddler walk the last .5 mile so she would get worn out too...but wasn't slowing me down the whole walk. And it looks like you live in AZ, so you don't have to wait for the 'warm months!'